Seat mechanism for through bore well heads

ABSTRACT

A retractable seat mechanism for a casing head comprising a plurality of arcuate segments and an actuating screw for each segment, wherein the screws are threaded inwardly to urge the segments from a retracted position until the segments drop into a pipe hanging position.

United States Patent Putch 1 51 July 25, 1972 [54] SEAT MECHANISM FOR THROUGH 3,155,401 1 1/1964 MLISOll ..285/DIG. 7 BORE WELL HEADS 3,334,923 8/1967 Putch ..285/18 2,354,929 8/1944 Rector et al.. ..285/143 1 lnvemofl Samuel Putch, Houston, 2,920,909 1 1960 Allen ..285/146 C C S J 7 3,017,931 1/1962 Jackson et al ..285/144 X [73] Ass'gnee FM ose 3,239,248 3/1966 Jones ..285/145 Filed! J y 1970 3,454,289 7/1969 Fowler ..285/144 [21] Appl' 59170 Primary Examiner-Dave W. Arola Attorney-F. W. Anderson, C. E. Tripp and W. W. Ritt [52] US. Cl ..285/144, 285/347 [51] Int. Cl ..F16l 21/00 [57] ABSTRACT [58] g q 95 3 5 5 5 A retractable seat mechanism for a casing head comprising a plurality of arcuate segments and an actuating screw for each segment, wherein the screws are threaded inwardly to urge the References Cited segments from a retracted position until the segments drop UNITED STATES PATENTS into a pipe hanging position.

4 Claims, 6 Drawing Figures United States Patent 1 3,679,238 Putch 1 July 25, 1972 BACKGROUND OF THE INVENTION The present invention relates to a well apparatus, and more particularly to a retractable casing suspension mechanism.

In oil well drilling operations it is common and sometimes necessary to develop the borehole in successively smaller diameter sections and line each section with casing. Usually a casing head is secured at ground level to the surface casing lining the first section of the borehole, and the successively smaller diameter strings of casing are then supported by hangers that rest on annular shoulders in the casing head bore. Since the shoulders are cast or machined in the bore, they are integral with the casing head and thus are not adjustable with respect to their diameter.

After the casing head and the blowout preventer stack have been installed, drilling of the lesser diameter portions of the borehole continues. In many instances oversize bits are required to drill the hole to the desired size, and because of the annular shoulders in the casing head bore there often is insufficient clearance to pass these bits through it. Several techniques have been used to solve this problem, one being the utilization of expandable bits that are passed through the casing head in contracted condition, and then expanded at the drilling level. However, the expandable bit often is undesirable because it frequently produces large cuttings which are difficult to remove from the hole, and if not removed these cuttings can clog the hole when cementing the casing in place. Also, valuable time is required to expand and contract these bits, thereby increasing the expense of drilling the well.

Another method requires starting with a larger casing head than ultimately required, thus providing the needed clearance for the oversized bits, and then changing to a smaller casing head and blowout preventer stack after the casing of lesser diameter has been installed and cemented. This method also has drawbacks, chiefly in the loss of valuable time, that is required to change the casing heads and the blowout preventers.

Other inventions have been directed to this problem, one such being described in U.S. Pat. No. 1,389,920 to Weaver. Weavers device involves a casing head with a series of four arcuate segments that are urged downwardly and inwardly on an inclined surface from a recessed position in the bore of the head, to present a cylindrical stepped portion for providing support for the casing hanger. However, the hanger support surface presented by this device is rather limited in size, and this device is not intended for pressure applications since no provision is made for packing off.

Two inventions of Penick, described in U.S. Pat. Nos. 2,086,43l and 2,254,752, are also directed to this problem. The devices of these patents each present a seat formed by the coaction of four arcuate segments urged inwardly of a well head by four actuator screws. The seat surface presented by these devices is limited in area and the segments themselves are given only limited support surfaces in the wall of the well head. These devices also have a tendency to jam in the retracted position from mud and cuttings that fill the recesses.

Another invention directed to a retractable supporting shoulder for a hanger is that of Fowler U.S. Pat. No. 3,438,653. Fowler describes a seat formed of four arcuate segments that are urged downwardly on an incline from a recessed position into an extended position to support a hanger and casing. The arcuate segments of this invention are actuated by either a hydraulic of pneumatic piston. Due to the positioning of the fluid bypass ducts it would be possible for cuttings which have been flushed from the borehole to lodge behind the segments, making segment retraction impossible. The location of the bypass ducts also increases the difficulty of packing off after suspending a casing in the well head. The seat mechanism of this Fowler invention also requires considerable space in the well head, thus increasing the overall size of the well head.

SUMMARY OF THE INVENTION The present invention is directed to a retractable device for suspension of piping within a casing head. The suspension device includes four quarter-circular seat segments having frusto-conical seat surfaces that are actuated by a series of four actuator. screws. The segments are held in a fully retracted or inoperative position in a first recessed groove in the casing head as drilling operations are being conducted. With the segments held in the retracted position, the casing head presents a straight-through, unobstructed bore. When it becomes necessary to suspend a casing from the casing head, the actuating screws are threaded inwardly to urge the segments toward the center of the head until the segments drop into a second recessed groove in the head. In this position the segments are in an end-to-end relationship and present a continuous, annular, frusto-conical seat surface for support of a pipe hanger having an annular shoulder that mates with this seat surface.

Accordingly, it is an object of this invention to provide a new and improved casing hanger seat mechanism for oil well drilling apparatus. Another object of this invention is to provide a seat mechanism which, when retracted, will provide a straight unobstructed bore through a well head to permit use of maximum diameter drills. A further object of the present invention is to provide a seat mechanism for use in a unitized well head construction which does not have to be changed through all drilling and pipe hanging operations.

Still further objects of the present invention are to provide: an economical seat mechanism that requires a minimum amount of space in a casing head; a retractable seat mechanism for suspension of piping in a casing head that cannot be jammed by mud or cuttings and is practically impossible to damage; a seat mechanism in a casing head wherein high compression loadings of the casing strings are borne by the casing head through compression loading of the seat segments, and not by seat actuating screws; and a seat mechanism that can be set or retracted without the use of special tools in a short time period.

These, together with other objects, will become apparent upon reference to the following description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevation of a casing head embodying the present invention, with parts broken away. a

FIG. 2 is a horizontal section of the casing head of FIG. 1 taken along line 2--2 of FIG. I, with parts removed.

FIG. 2A is an enlarged perspective at the central portion of a seat segment showing the T-shaped slot.

FIG. 3 is an enlarged view of one of the actuating screws as shown in FIG. 1.

FIG. 4 is a side elevation of the casing head embodying the seat mechanism in a retracted position, with parts removed.

FIG. 5 is a side elevation of the casing head embodying the seat mechanism of the present invention in supporting relation to a slip type hanger, with parts removed.

DESCRIPTION OF THE PREFERRED EMBODIMENT With reference to FIGS. 1, 2 and 4, the present invention involves a seating mechanism 10 in the longitudinal bore ll of a casing head 12, for movement between a released or retracted position (FIG. 4) and a set or pipe hanging position (FIG. I). The casing head 12, which is supported on a surface casing I4 that is cemented in place, is preferably of the unitized type that permits landing and packing off all casing and tubing strings in a single well head unit.

The seating mechanism 10 is comprised of four arcuate seat elements or segments 16 disposed in a released or retracted position in a first recessed groove 18 in the casing heads bore 1 l, the segments being actuated or moved by four seat actuating screws 22 into their set or extended position in a second recessed groove 20 for support of a casing or tubing hanger. The first recess or groove 18 has a radial annular upper shoulder 18a projecting out from the casing heads bore 11, a first cylindrical retaining wall or stop surface 18b depending from the upper shoulder 18a, and a first frusto-conical guide wall 18c extending downwardly and inwardly from the stop surface 181). Directly beneath and in communication with the first recess or groove 18 is a second recess or groove 20 for support of the segments 16 in their set or pipe hanging position. The second recess 20 is, as is the first recess, radially removed from the bore 11 such that there are no projections extending into the bore 11 that will interfere with the use of required drill sizes. With further reference to FIG. 4, the second recess 20 includes a second cylindrical retaining wall 20a depending from the first frusto-conical guide wall 186 and a second frusto-conical guide wall 20b projecting downwardly and inwardly of the casing head 12 from the retaining wall 20a.

As illustrated by FIG. 2, each of the four arcuate segments 16 represents a quarter-circle, such that when the segments are in the set or pipe hanging position (FIG. 1) their surfaces 16g present a continuous circular supporting surface or shoulder 17. A section through the central portion of a segment 16 (FIGS. 1 and 4) illustrates the preferred configuration of the segments. Each segment 16 includes a stop surface or arcuate retaining wall 16a for engagement with the first retaining wall 18b when the segments are in the released or retracted position, and for engagement with the second retaining wall 20a when the segments are in the set or pipe hanging position. A centrally disposed T-shaped axial slot 16b extends the full height of the stop surface 16a of each segment for sliding engagement with a cylindrical projection 23 on each of the segment actuation screws 22.

Depending downwardly and inwardly from the stop surface 16a is a frusto-conical surface 16c which interengages the first frusto-conical guide wall 180 in the casing head in the released position, and which interengages the second frusto-conical guide wall 20b when the segment 16 has been dropped into the set or pipe hanging position. A radial annular surface 16d connects the frusto-conical surface 160 and a bevelled surface l6e that projects upwardly and inwardly of the casing head 12. A second arcuate retaining wall 16f, parallel to the stop surface 160, extends upwardly from the bevelled surface 16c and intersects a frusto-conical seat surface 16g. The frusto-conical seat surface 16g is parallel to and coextensive with the frustoconical surface 16c. With this design the total casing load on the seat segments is transmitted to and borne by the casing head. In the set position (FIGS. 1, 2, 3, and the arcuate segments 16 are in an end-to-end relationship and present a continuous surface 17 for seating a pipe hanger, as stated previously.

The actuating screws 22 are mounted in internally threaded sleeves 24 that are welded into ports 26 at 90 intervals about the casing head 12. The outer end of each of the sleeves is increased in diameter to form a boss 24a. This boss 24a is utilized to give increased support to the actuating screws 22 without increasing the casing head wall thickness. As shown best in FIGS. 1 and 3, each of the actuating screws 22 in the preferred embodiment includes the cylindrical projection or tip 23, a reduced diameter cylindrical portion 28 connecting the projection and an outer end 30 of a cylindrical inner portion 32, a cylindrical intermediate portion 34, a threaded portion 36 having right handed threads for engagement with internal threads of the sleeve 24, a stop spring 38 installed in a groove adjacent the outer end of the threaded portion 36, a cylindrical rim 40 adjacent the stop spring 38, and a wrench portion 42 having a plurality of flats projecting from the rim.

Each of the actuating screws 22 is movable between a retracted position (FIG. 4) with the outer end 30 of the cylindrical inner portion 32 in planar alignment with the stop surface 18b of the outer recess 18, and a set position (FIGS. 1-3) with the outer end 30 in planar alignment with the second cylindrical retaining wall a. Once in the retracted position,

the screw is inhibited from further retraction by the interengagement of an outer surface 23a of the cylindrical projection 23 and an inner surface 16h of the segments T-shaped slot 16b. When in the set position the screw 22 is limited against further travel into the casing head by the stop spring 38 that bears against the outer surface 24b of the sleeve 24.

To effect a seal between the screw 22 and the sleeve 24, the inner portion of each screw has an annular groove 46, and an annular packing or seal 48 is positioned within this groove. As shown in FIG. 3, the screw 22 has an axial bore 50 provided with a closed inner end 52 and an outer threaded portion 54 opening through the screws wrench portion 42. A check valve 56 is threaded into the portion 54 against a shoulder 58 of the bore, and an injector plug 60 is threaded into the outer end of the portion 54 in spaced relation to the check valve 56, the plug 60 having an outwardly opening, wrench-receiving socket 62. A stick of extrudable plastic material 64 is positioned in the bore 50 between the check valve 56 and the plug 60. The screw'22 also has a plurality of radial passages 66 providing communication between the axial bore 50 and the groove 46. Thus by threading the plug 60 inwardly, plastic material is extruded through the check valve 56 into the bore 50 and the radial passages 66, where it exerts pressure outward against the seal 48 to maintain it in fluid tight contact with wall 240 of the sleeve 24. Whenever it is desired to increase the sealing effect between the seal 48 and the wall 246, the plug 60 is threaded in further to extrude more plastic and to increase the radial pressure on the seal. If necessary, additional plastic material can be inserted into the bore 50 between the check valve 56 and the plug 60. The check valve 56, of course, operates to prevent return flow of plastic material.

In reference to FIG. 4, during drilling operations the arcuate segments 16 are disposed in the first recess 18 with the stop surface 16a of the segments 16 contacting the stop surface 18b of the first recess, and with the actuating screws 22 in their fully retracted position. With the segments 16 held in the fully retracted position, the diameter D1 as defined by the segments is the same dimension as the diameter D2 of the casing heads bore 11, so that no obstruction is presented by the retracted segments 16. Therefore, any bit that can be inserted into the bore 11 will pass by the retracted segments 16, thereby facilitating the use of bits limited in size only by the diameter of the bore itself.

As drilling is completed, and it becomes necessary to support a casing string from the casing head, the arcuate segments 16 are moved into their set position to support a casing hanger 68 (FIG. 1). The actuation of the segments from the retracted to the set position is accomplished by inwardly threading each of the actuating screws 22 with a wrench until the stop spring 38 contacts the outer surface 24b of the sleeve 24. At this point the frusto-conical surface of the segment has moved out of engagement with the first frusto-conical guide wall 18c and has dropped under its own weight into position in the second recess 20. With all four segments positioned in the lower recess, a continuous seat surface or shoulder 17 is presented for support of the casing hanger 68.

The casing hanger 68, to which a string of casing 70 is attached, has an annular shoulder 72 about its periphery which interengages the seat segments 16. The shoulder 72 includes a frusto-conical surface 72a that seats on the frusto-conical seat surface 17 presented by the segments, and a cylindrical wall 72b that abuts and is coextensive with the second arcuate retaining wall 20a when the hanger 68 is supported on the shoulder.

After the hanger 68 has been landed on the shoulder an annular pack-off 73 is installed between the hanger and the casing head 12, and drilling for the next casing string 74 of smaller diameter is begun. Casing string 74 is then supported in the casing head by a hanger 76, and packed off and held down by a packoff 78.

Once the hanger 68 has been landed on the shoulder 17, cementing and flushing operations can be conducted without damage or interference with the seat mechanism. Fluid is simply forced down the casing 70 with the upward return flow issuing from four ports 79. Since the seat mechanism presents a substantially continuous annular barrier or ring in the set position, the mechanism can't be jammed by mud or cuttings being flushed from the well.

Although the hanger 68 illustrated in FIG. 1 is of the type that attaches by means of threads to the end of the casing string 70, the seat mechanism can also be used with a slip type hanger 80, as illustrated in FIG. 5. The hanger 80 comprises a slip bowl 82 and slips 84, and the slip bowl has a shoulder 82:: which interengages the seat surface or shoulder 17 presented by the segments. The shoulder 82a has a frustoconical wall 82b which interengages the segments frusto-conical seat surfaces 16g, and a cylindrical retaining wall 821: which abuts the retaining walls 16f of these segments. To land a casing string 81 with this type of hanger, the slip bowl 82 is placed on the seat formed by segments 16, the casing is lowered to the desired position, and the slips 84 are then lowered into place in the slip bowl 82 to tightly grasp the casmg.

Thus it can be seen that the present invention presents an economical seat mechanism that requires a minimum amount of space in a casing head; that cannot jam and is practically impossible to damage; that transmits the full load of suspended casings to the casing head; that is fully retractable to give a straight bore through a casing head which will allow for the use of oversize bits; that can be set or unset without special tools in a short time period; and that is especially useful for unitized well head constructions.

Although the best mode contemplated for carrying out the present invention has been herein shown and described, it will be apparent that modification and variation may be made without departing from what is regarded to be the subject matter of the invention.

What is claimed is:

1. Apparatus for suspending a string of pipe from a pipe hanger within a well, including:

a. a casing head having a straight-through bore, a first recessed groove in the bore with a frusto-conical surface disposed radially outward of the bore, a second recessed groove in the bore with a frusto-conical surface disposed radially outward of the bore and below the first recessed groove, a first cylindrical retaining wall ascending from the frusto-conical surface of the first recessed groove, and a second cylindrical retaining wall connecting the frustoconical surfaces of the first and second recessed grooves,

b. a plurality of seat segments each having an axially extending T-shaped slot and a lower frusto-conical surface, and

c. actuating screws each having a first end from which extends a projection with a T-shaped cross-section in sliding engagement with one of the seat segments, said screws provided for manual turning to urge the segments inwardly from a fully retracted position in the first recessed groove and downwardly along the frusto-conical surface of said first recessed groove until the segments drop into a set position in the second recessed groove to form a continuous seat surface for support of the pipe hanger.

2. Apparatus for suspending a string of pipe from a pipe hanger within a well, including:

a. a casing head having a straight-through bore, a first recessed groove in the bore with a frusto-conical surface disposed radially outward of the bore, a second recessed groove in the bore with a frusto-conical surface disposed radially outward of the bore and below the first recessed groove, a first cylindrical retaining wall ascending from the frusto-conical surface of the first recessed groove, and a second cylindrical retaining wall connecting the frustoconical surfaces of the first and second recessed grooves, b. a plurality of seat segments each having an axially extending T-shaped slot and co-extensive upper and lower frustoconical surfaces, and c. actuating screws each having a first end from wind] extends a projection with a T-shaped cross section for sliding engagement with the T-shaped slot in one of said seat segments, said screws provided for manual turning to urge the segments inwardly from a fully retracted position in the first recessed groove until the segments drop into a set position in the second recessed groove to form a continuous frusto-conical seat surface for support of the pipe hanger, the first end of each screw presenting an axially extending surface, said surface being coplanar with the first cylindrical retaining wall when the segments are fully retracted, and said surface being coplanar with the second cylindrical retaining wall when the segments have dropped into the set position in the second recessed groove.

3. The apparatus of claim 2 wherein four segments form the continuous frusto-conical seat surface.

4. A well apparatus for suspending a pipe within a well,

comprising:

a. a casing head having an unobstructed longitudinal bore, an upper recessed groove radially removed from the bore and comprised of a frusto-conical portion and a cylindrical portion ascending from said frusto-conical portion, and a lower recessed groove radially removed from the bore and comprised of a frusto-conical portion and a cylindrical portion extending from the upper end of the lower grooves frusto-conical portion to the lower end of the upper grooves frusto-conical portion;

b. a plurality of arcuate segments in the casing head, each segment having an upper frusto-conical seat surface, a coextensive and parallel lower frusto-conical seat surface, and an axially extending slot T-shaped in cross-section;

c. actuating screws mounted transverse to the bore of the casing head for moving the segments between an inoperative, retracted position in the upper recessed groove and an operative pipe-supporting position in the lower recessed groove, said screws being threaded inwardly after a borehole has been drilled to move the segments from retracted position in the upper groove until they drop into engagement with the lower groove wherein they cooperate to present a continuous frusto-conical seat surface, each of said screws also having a first end from which a cylindrical projection with a T-shaped cross section extends for sliding engagement with the T-shaped slot of one of said segments, and wherein the first end of each screw presents an axially extending surface, said surface being coplanar with the cylindrical portion of the upper recessed groove when the segments are fully retracted, and said surface being coplanar with the cylindrical portion of the lower recessed groove when the segments have dropped into the operative pipe-supporting position in the lower recessed groove; and

d. a pipe hanger, from which a string of pipe is suspended, having a frusto-conical surface for interengagement with the frusto-conical seat surface presented by the segments, said hanger being lowered onto the frusto-conical seat surface after the segments have been dropped into supporting position in the lower recessed groove. 

1. Apparatus for suspending a string of pipe from a pipe hanger within a well, incluDing: a. a casing head having a straight-through bore, a first recessed groove in the bore with a frusto-conical surface disposed radially outward of the bore, a second recessed groove in the bore with a frusto-conical surface disposed radially outward of the bore and below the first recessed groove, a first cylindrical retaining wall ascending from the frustoconical surface of the first recessed groove, and a second cylindrical retaining wall connecting the frusto-conical surfaces of the first and second recessed grooves, b. a plurality of seat segments each having an axially extending T-shaped slot and a lower frusto-conical surface, and c. actuating screws each having a first end from which extends a projection with a T-shaped cross-section in sliding engagement with one of the seat segments, said screws provided for manual turning to urge the segments inwardly from a fully retracted position in the first recessed groove and downwardly along the frusto-conical surface of said first recessed groove until the segments drop into a set position in the second recessed groove to form a continuous seat surface for support of the pipe hanger.
 2. Apparatus for suspending a string of pipe from a pipe hanger within a well, including: a. a casing head having a straight-through bore, a first recessed groove in the bore with a frusto-conical surface disposed radially outward of the bore, a second recessed groove in the bore with a frusto-conical surface disposed radially outward of the bore and below the first recessed groove, a first cylindrical retaining wall ascending from the frusto-conical surface of the first recessed groove, and a second cylindrical retaining wall connecting the frusto-conical surfaces of the first and second recessed grooves, b. a plurality of seat segments each having an axially extending T-shaped slot and co-extensive upper and lower frusto-conical surfaces, and c. actuating screws each having a first end from which extends a projection with a T-shaped cross section for sliding engagement with the T-shaped slot in one of said seat segments, said screws provided for manual turning to urge the segments inwardly from a fully retracted position in the first recessed groove until the segments drop into a set position in the second recessed groove to form a continuous frusto-conical seat surface for support of the pipe hanger, the first end of each screw presenting an axially extending surface, said surface being coplanar with the first cylindrical retaining wall when the segments are fully retracted, and said surface being coplanar with the second cylindrical retaining wall when the segments have dropped into the set position in the second recessed groove.
 3. The apparatus of claim 2 wherein four segments form the continuous frusto-conical seat surface.
 4. A well apparatus for suspending a pipe within a well, comprising: a. a casing head having an unobstructed longitudinal bore, an upper recessed groove radially removed from the bore and comprised of a frusto-conical portion and a cylindrical portion ascending from said frusto-conical portion, and a lower recessed groove radially removed from the bore and comprised of a frusto-conical portion and a cylindrical portion extending from the upper end of the lower groove''s frusto-conical portion to the lower end of the upper groove''s frusto-conical portion; b. a plurality of arcuate segments in the casing head, each segment having an upper frusto-conical seat surface, a co-extensive and parallel lower frusto-conical seat surface, and an axially extending slot T-shaped in cross-section; c. actuating screws mounted transverse to the bore of the casing head for moving the segments between an inoperative, retracted position in the upper recessed groove and an operative pipe-supporting position in the lower recessed groove, said screws being threaded inwardly after a borehole has been drilled to move the segments from retracted position in the upper groove until they Drop into engagement with the lower groove wherein they cooperate to present a continuous frusto-conical seat surface, each of said screws also having a first end from which a cylindrical projection with a T-shaped cross section extends for sliding engagement with the T-shaped slot of one of said segments, and wherein the first end of each screw presents an axially extending surface, said surface being coplanar with the cylindrical portion of the upper recessed groove when the segments are fully retracted, and said surface being coplanar with the cylindrical portion of the lower recessed groove when the segments have dropped into the operative pipe-supporting position in the lower recessed groove; and d. a pipe hanger, from which a string of pipe is suspended, having a frusto-conical surface for interengagement with the frusto-conical seat surface presented by the segments, said hanger being lowered onto the frusto-conical seat surface after the segments have been dropped into supporting position in the lower recessed groove. 